Conditional access (CA) is a technique for limiting the access of content (e.g., audiovisual works such as movies) to authorized users. For example, CA systems have been developed for cable TV and non-cable TV including digital television (DTV). In a CA system for digital television, the media content is scrambled (encrypted) using a standard algorithm before broadcasting. The key used for scrambling/descrambling the media content in a CA system is called a control word (CW). The control word is securely provided to the subscribers through entitlement control messages and entitlement management messages. A security device uses the control word to descramble (decrypt) the received media content.
A CableCARD is a removable security device for conditional access and service signal demodulation in a cable television system. A CableCARD is typically in a PCMCIA or PC card form factor. When inserted in a set top box, television or other device, a CableCARD enables delivery of digital video pay programming and other services, such as in a cable television system in accordance with an OpenCable specification. CableCARDs are typically provided by the cable operator or cable provider to subscribers.
One technique for limiting the diffusion of media content in digital television signals that are broadcast over the air in-the-clear involves the use of a broadcast flag. A data tag, called broadcast flag, can be used to mark a program. If a program is marked with the broadcast flag, any Federal Communications Commission (FCC) rule compliant device must refuse to allow the broadcast flagged program to be exposed in-the-clear on any of the device digital output. See, for example, FCC Report and Order and Further Notice of Proposed Rulemaking, MB Docket No. 02-230, In The Matter of Digital Broadcast Content Protection, released Nov. 4, 2003.